The development of new synthetic fibers for making fiber-rubber composites has resulted in a continuing problem of bonding the new fibers to rubber. Adhesive compositions, based on resorcinol and formaldehyde were discovered early in the development of the art and achieved commercial acceptance for bonding nylon and rayon fiber to rubber but the adhesives acceptable for bonding rayon and nylon to rubber are not entirely satisfactory for polyester fiber. The adhesives of the present invention are particularly applicable to bonding polyester fiber to rubber. Alkenylresorcinols have heretofore been proposed as fiber bonding agents but are not to be confused with the compositions of the present invention which are polymeric and essentially saturated.
In the preferred method of practicing the invention, the unsaturate-resorcinol polymer is used in conjunction with conventional bonding agents to achieve improved adhesion as compared to the conventional treatment alone. For example, a composition comprising a resorcinol-formaldehyde condensation product and a butadiene-styrene-vinylpyridine latex, called RFL is commonly used to bond synthetic fibers to rubber. The unsaturate-resorcinol polymer resins may advantageously replace the resorcinol in the RFL system to secure improved adhesion.